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[PATCH] vmi: cpu cycles fix

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In order to share the common code in tsc.c which does CPU Khz calibration, we
need to make an accurate value of CPU speed available to the tsc.c code.  This
value loses a lot of precision in a VM because of the timing differences with
real hardware, but we need it to be as precise as possible so the guest can
make accurate time calculations with the cycle counters.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Zachary Amsden 2007-03-05 00:30:36 -08:00 committed by Linus Torvalds
parent 6cb9a8350a
commit 1182d8528b
7 changed files with 17 additions and 2 deletions
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1
arch/i386/kernel/paravirt.c
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@ -522,6 +522,7 @@ struct paravirt_ops paravirt_ops = {
.read_tsc = native_read_tsc,
.read_pmc = native_read_pmc,
.get_scheduled_cycles = native_read_tsc,
.get_cpu_khz = native_calculate_cpu_khz,
.load_tr_desc = native_load_tr_desc,
.set_ldt = native_set_ldt,
.load_gdt = native_load_gdt,

2
arch/i386/kernel/tsc.c
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@ -117,7 +117,7 @@ unsigned long long sched_clock(void)
return cycles_2_ns(this_offset);
}
static unsigned long calculate_cpu_khz(void)
unsigned long native_calculate_cpu_khz(void)
{
unsigned long long start, end;
unsigned long count;

1
arch/i386/kernel/vmi.c
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@ -874,6 +874,7 @@ static inline int __init activate_vmi(void)
paravirt_ops.setup_secondary_clock = vmi_timer_setup_secondary_alarm;
#endif
paravirt_ops.get_scheduled_cycles = vmi_get_sched_cycles;
paravirt_ops.get_cpu_khz = vmi_cpu_khz;
}
if (!disable_noidle)
para_fill(safe_halt, Halt);

10
arch/i386/kernel/vmitime.c
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@ -177,6 +177,15 @@ unsigned long long vmi_get_sched_cycles(void)
return read_available_cycles();
}
unsigned long vmi_cpu_khz(void)
{
unsigned long long khz;
khz = vmi_timer_ops.get_cycle_frequency();
(void)do_div(khz, 1000);
return khz;
}
void __init vmi_time_init(void)
{
unsigned long long cycles_per_sec, cycles_per_msec;
@ -206,7 +215,6 @@ void __init vmi_time_init(void)
(void)do_div(cycles_per_alarm, alarm_hz);
cycles_per_msec = cycles_per_sec;
(void)do_div(cycles_per_msec, 1000);
cpu_khz = cycles_per_msec;
printk(KERN_WARNING "VMI timer cycles/sec = %llu ; cycles/jiffy = %llu ;"
"cycles/alarm = %llu\n", cycles_per_sec, cycles_per_jiffy,

2
include/asm-i386/paravirt.h
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@ -95,6 +95,7 @@ struct paravirt_ops
u64 (*read_tsc)(void);
u64 (*read_pmc)(void);
u64 (*get_scheduled_cycles)(void);
unsigned long (*get_cpu_khz)(void);
void (*load_tr_desc)(void);
void (*load_gdt)(const struct Xgt_desc_struct *);
@ -275,6 +276,7 @@ static inline void halt(void)
#define rdtscll(val) (val = paravirt_ops.read_tsc())
#define get_scheduled_cycles(val) (val = paravirt_ops.get_scheduled_cycles())
#define calculate_cpu_khz() (paravirt_ops.get_cpu_khz())
#define write_tsc(val1,val2) wrmsr(0x10, val1, val2)

2
include/asm-i386/timer.h
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@ -7,6 +7,7 @@
void setup_pit_timer(void);
unsigned long long native_sched_clock(void);
unsigned long native_calculate_cpu_khz(void);
/* Modifiers for buggy PIT handling */
extern int pit_latch_buggy;
@ -17,6 +18,7 @@ extern int recalibrate_cpu_khz(void);
#ifndef CONFIG_PARAVIRT
#define get_scheduled_cycles(val) rdtscll(val)
#define calculate_cpu_khz() native_calculate_cpu_khz()
#endif
#endif

1
include/asm-i386/vmi_time.h
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@ -50,6 +50,7 @@ extern void __init vmi_time_init(void);
extern unsigned long vmi_get_wallclock(void);
extern int vmi_set_wallclock(unsigned long now);
extern unsigned long long vmi_get_sched_cycles(void);
extern unsigned long vmi_cpu_khz(void);
#ifdef CONFIG_X86_LOCAL_APIC
extern void __init vmi_timer_setup_boot_alarm(void);